Molded Catheter Tip

ABSTRACT

A catheter has extruded length of tubing and an injection molded tip that facilitates insertion of the catheter into the body. The catheter is fabricated by the steps of providing the tubing, for example, by extruding the tubing from a thermoplastic resin cutting the tubing to the desired length, inserting a plug into the tubing, inserting one end of the tubing into an injection mold cavity, creating and forming a tip in an injection molding step, and demolding the tubing with the formed tip.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/980,412, filed Apr. 16, 2014, the disclosure ofwhich is incorporated by reference herein.

FIELD OF THE DISCLOSURE

The present disclosure is directed generally to a catheter assembly anda method of making a catheter assembly.

BACKGROUND

A catheter is a flexible, hollow tube which can be inserted into thebody for the introduction or removal of fluids. A common, but by nomeans exclusive, type of catheter is a urinary catheter which is used bythose who suffer from various abnormalities of the urinary system. Aurinary catheter is inserted through the urethra for draining urine fromthe bladder.

To facilitate insertion of a catheter into a body cavity, it isdesirable to have a formed tip on one end of the catheter tube. A verycommon way to make this structure is to extrude tubing from athermoplastic polymer material, and cut it to the desired length. One ofthe cut ends is then formed into a tip shape in a secondary operation,for example, by forcing the cut end into a heated die that has thedesired tip shape.

Extruding the tubing section of the catheter is desirable because it isa relatively inexpensive process, and it allows for good control of thetube's outside diameter and wall thickness. Forming a tip by pushing atube cut end into a heated die has some disadvantages, however. The diemust be hot during the pushing step, in order to soften the tubematerial so it will form. Then the die must be cooled to allow releaseof the formed part. For the next cycle, the die must now be reheated.These die heating and cooling steps limit how short the process cycletime can be. Another problem with the heated die forming method concernscatheters having multiple layers. It is desirable to have a hydrophiliccoating on the exterior of the catheter to add lubricity. Such coatingsare not compatible with all tube materials so it is known to co-extrudethe tubing from two layers of different materials, the outer of whichreadily accepts a hydrophilic coating. The coating is applied afterformation of the tip. A problem with the heated die tip formation methodarises because the heating process distorts the layers at the end of thetube. The desired outer layer material, which accepts the coating, maynot remain on the outside of the tip after heated die formation of thetip. That is, the inner and outer tubing layers tend to become somewhatdistorted during heated die tip formation with the result that some ofthe inner tubing layer material may end up exposed on the exterior ofthe formed tip. This can lead to failure of the hydrophilic coating toadhere fully to the tip.

SUMMARY

In one aspect, the present disclosure concerns a catheter whose shaft isformed from a tube, such as, for example, an extruded tube. A formed tipthat facilitates insertion of the catheter into the body is fabricatedon one end of the tube by an insert molding process.

A catheter for introduction into a body cavity may be fabricated by thefollowing steps: 1) a tube is extruded from a thermoplastic polymermaterial, and cut to the desired catheter length; 2) one end of thelength of tubing is inserted into an injection mold cavity; 3) a formedtip is created and bonded to the tubing end in an injection moldingstep; 4) the tubing with the formed tip is demolded; and 5) if desired,a funnel can be attached to the other end of the tubing by conventionalmethods such as solvent bonding, spin welding, hot melt bonding, or bythe non-conventional step of injection molding the funnel onto thetubing.

The mold for the tip formation can be gated at the apex of the tip, anda small depression can be designed into this apex so that any gateresidue in the formed part is not protruding from the surface of thepart.

The injection molding steps are further characterized in that a plug ispress fit into the lumen at one end of the tubing just prior toinserting that end into the injection mold. During the injection moldingstep that forms the tip on the end of the tube the plug acts as amolding shut-off to ensure proper filling of the mold. In onealternative embodiment the plug can be pre-heated, to reduce the amountof heat transfer from the injected thermoplastic polymer material neededfor proper bonding to the plug and to the tubing walls.

In total this is a novel way to provide a formed tip on the end of anextruded tube. The strategy of using a thermoplastic plug as apre-molding insert to provide injection shut-off is believed to benovel. The idea of injection molding on to a pre-heated plug, as an aidto good bonding, is believed to be novel as well. The injection-moldedtip also maintains the integrity of a multi-layer tube construction,assuring that the outer layer material of the tubing remains on theexterior of the catheter where it can accept a hydrophilic coating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an end portion of atubing and tip of a catheter assembly according to the presentdisclosure.

FIG. 2 is a cross-sectional view similar to FIG. 1 showing an alternateembodiment of the tubing which has a dual layer construction.

FIG. 3 is a cross-sectional view similar to FIG. 2 showing an alternateembodiment further including a hydrophilic coating.

FIG. 4 is a diagrammatic cross-sectional view of a tubing end portionand plug inserted into the cavity of a mold, ready for injection moldingof the tip.

FIG. 5 is a cross-sectional view similar to FIG. 4 showing an alternate,slightly protruding axial position for the plug.

FIG. 6 is a cross-sectional view similar to FIG. 4 showing a furtheralternate, slightly recessed axial position for the plug.

FIG. 7 is a cross-sectional view of a tip on an enlarged scale toillustrate the depression in the end of the tip.

FIGS. 8,9 and 10 are cross-sectional views through an end portion oftubing prior to injection molding but after insertion of a plug, eachshowing an alternate embodiment of a plug shape.

FIG. 11 is a cross-sectional view similar to FIG. 1, showing a furtheralternate embodiment having a plug located at an axial position wellrecessed from the end face of the tubing, the plug location permittingformation of a stubshaft on the tip.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure is directed to a catheter and a method of makingit, the method including the steps of cutting tubing to the desiredlength, inserting a plug into one end of the tubing and injectionmolding a tip onto the plugged end of the tubing. FIG. 1 illustrates anend portion of the catheter 10 according to the present disclosure. Thecatheter 10 has tubing 12 which is cut to length to define an endportion 14 which terminates at a radial end face 16. Tubing 12 may bemade by any suitable process, such as, for example, by an extrusionprocess. As is conventional, the tubing 12 defines an axial lumen 18that extends throughout the length of the tubing 12. There is also aradial eyelet 20 defined in one wall and in communication with the lumen18. For a urinary catheter, lumen 18 would serve as a urinary lumen withurine draining into the lumen 18 through the eyelet 20. A plug 22 isprovided of a suitable material, e.g., the main tubing wall componentmaterial. The plug 22 is sized to be insertable into the tubing lumen 18with an interference fit. In its simplest form, the plug 22 can be a cutlength of an extruded rod that is just larger in diameter than thetubing lumen 18. In an alternative form, the plug can be amicro-injection molded part, and can have a taper on one end, orpreferably on both ends, to aid in the insertion process. In embodimentswherein the plug has one or more tapered portions, it will be understoodthat a portion of the plug 22 will have a maximum outer diameter atleast as large as the inside diameter of the lumen 18, thus assuring thelumen 18 will be completely blocked during injection molding of the tip24.

The plug 22 may be inserted into the lumen 18 at the end portion 14 ofthe tubing 12. This end portion 14 is inserted into an injection mold. Aformed tip 24 is then injection molded onto the end portion 14 of thetubing 12 using a mold as shown in FIG. 4. In FIG. 4 the end portion 14of the tubing 12 is inserted into a mold. A first half of the mold isshown at 26. It will be understood that a second mold half, not shownbut largely a mirror image of the first mold half (with the mirror planebeing the plane of the paper of the drawing), would be used in theinjection molding process, although preferably the mold halves areintegral. That is, they are not necessarily made to be separable,although they could be. Together the mold halves define a cavity 28. Thecavity 28 opens to the exterior of the mold at an opening 30 forreceiving the end portion 14 of the tubing 12. The cavity 28 has aninner surface 32 that has the size and shape of the finished tip 24.Surface 32 optionally includes a slight bulge at 34 that will create adepression in the extreme end of the tip 24 as will be explained furtherbelow. A sprue 36 extends through the mold and forms a passagewaythrough which molten thermoplastic polymer material can be introducedinto the cavity 28.

When molten thermoplastic polymer material is injected into the cavity28 the plug 22 and radial end face 16 serve as a stop for the injectedthermoplastic polymer material; in a sense the plug 22 and end face 16become one wall of the injection mold while the inner surface 32 formsthe other wall. This ensures that the mold cavity 28 will fill properly,resulting in a well formed tip 24 of controlled geometry.

The material for injection molding should be one that is compatible withthe tubing material, to ensure good bonding between the molded tip 24and the tubing 12. Because the plug 22 is made of a suitable material,with proper selection of injection molding parameters, a strong bondforms between the plug 22 and the injected tip material along aplug-to-tip bond line 37. Likewise a strong bond forms between theinjected tip material and the end face 16 of the tubing 12. After theinjected tip material cools, optionally the mold halves are separatedand the tubing and tip are removed from the cavity 28. Alternatively,the mold may be one piece, and the tubing 12 with tip 24 may just bepulled free of the mold. The result is a formed tip 24 of desiredgeometry that is integral with the end 14 of the tubing 12.

In one alternate embodiment of the process, the plug 22 is pre-heatedbefore inserting it into the tubing end 14, just prior to insertion ofthe tube into the injection mold. The plug will then provide a source ofheat to heat the tubing walls, and in all less heat transfer from theinjected thermoplastic polymer material will be needed to create thedesired good bonding between the injected thermoplastic polymer materialtip, the plug, and the tubing end face. Using the strategy ofpre-heating the plug will reduce the melt temperature required to ensuregood bonding between the injected thermoplastic polymer material tip,the plug, and the tubing end face, and may also reduce the requiredcycle time for the tip molding process.

FIG. 2 illustrates an alternate embodiment of a catheter 38 having adifferent kind of tubing. In this embodiment the tubing 40 has a duallayer construction including an inner wall 42 and an outer wall 44. Thetubing 40 may be made by coextrusion wherein inner wall 42 and outerwall 44 are different materials. Eyelet 46 extends through both walls.The radial end face 48 includes both walls and is covered by the tip 50.In this embodiment, the outer wall 44, the plug 22 and the tip 50 may bemade of the same or similar materials. Alternatively, the plug 22 may bemade of material the same or similar to that of the inner wall 42.

FIG. 3 shows an alternate embodiment wherein the catheter 38 of FIG. 2has added to it an outer hydrophilic coating 52. The coating 52surrounds both the outer wall 44 and the tip 50. The coating 52 may beof the type commonly used to increase the lubricity of the catheter. Thetip material is preferably the same as the outer wall material so theywill both accept the outer hydrophilic coating 52.

FIGS. 5 and 6 are similar to FIG. 4 but show alternate axial positionsfor the plug 22. In FIG. 5 the plug 22 protrudes axially beyond theradial end face 16. In FIG. 6 the plug 22 is recessed somewhat from theradial end face 16.

In the enlarged view of FIG. 7 it can be seen that the bulge 34 in themold cavity's inner surface 32 creates a dimple or depression 54 in theapex of the tip 24. Since the sprue 36 is gated at the apex of the tip,any gate residue in the formed tip is not protruding from the surface ofthe tip but instead lies within the depression 54 where it will notaffect a user of the catheter.

FIGS. 8, 9 and 10 illustrate alternate forms that the plug could take.FIG. 8 shows a plug 56 having a rounded inner end that assists withinsertion into the lumen 18 of the tubing 12. FIG. 9 shows a plug 58that is rounded on both ends so either one can be readily inserted intothe lumen. FIG. 10 shows a spherical plug 60.

FIG. 11 shows yet another alternate embodiment wherein prior to moldingthe plug 22 is axially recessed into the lumen nearly to the eyelet 20.With this axial placement of the plug injected thermoplastic polymermaterial will enter the lumen until it meets the plug 22, therebyforming a stubshaft 62 that is integral with the tip 64. This providesenhanced stability of the tip on the tubing 12. The stubshaft 62 joinsthe plug at the plug-to-tip bond line 66.

The mold desirably does not have any parting line, rather the part willdemold due to the taper of the tip and material shrinkage on cooling. Apossible alternate configuration during the molding step is to have thelong axis of the tube protruding from the mold vertically. In thisconfiguration gravity will help to accomplish the desired result of themold filling before thermoplastic polymer material enters the tubelumen. The amount of injected thermoplastic polymer material enteringthe tube lumen is then controlled by controlling molding shot size.

In the catheter of the present disclosure the thermoplastic polymermaterial that will be injection molded to the end of the extruded tubecan be kept always hot, in the molder feed system. A mold cooling stepis needed, but only the heat transferred to the mold by the injectedthermoplastic polymer material needs to be carried away. This willresult in a shorter cycle time compared to the conventional tip formingprocess.

Another advantage of the catheter of the present disclosure is that thetotal length of the tipped catheter can be highly controlled. In theconventional process, the tip formed on the end of the tubing will havea much higher length variation. This variability in the tipped catheterlength can cause problems in subsequent catheter converting steps.

A further advantage of the catheter of the present disclosure is thatthe proposed process will work well with coextruded tubing, such asshown in FIG. 2 for example. This tubing 40 may have a thin outer wall44 present for accepting a hydrophilic coating, such as at 52 in FIG. 3.In such an embodiment, the inner wall 42 may be made from a materialthat has desirable mechanical characteristics for a urinary catheter,e.g., desired stiffness/flexibility, such materials may include forexample thermoplastic resins such as olefins, particularlypolyethylenes, polypropylenes, polyvinylchlorides,polytetrafluoroethylenes, polyvinylacetates, polystyrenes, polyesters,polyurethane, polyamides, ethylene vinyl acetate copolymers, copolymersof ethylene with other comonomers such as acrylic acid, or combinationsthereof. The outer wall 44 and tip 50 may be made from a material thatis conducive to bonding or receiving the hydrophilic coating. The outerwall 44 and tip 50 may be for example made from a water-swellablepolymer such as water-swellable polyamide-base copolymers,water-swellable polyester-based copolymers or water-swellableurethane-based copolymers. Other polymers may include blends of thesewater swellable thermoplastic polymers with non-water swellablethermoplastic polymers. Polymers can be utilized that have functionalgroups selected to provide bonding to specific coating chemistries.Functional groups such as carboxyl, amine, hydroxyl, and other knownreactive groups can be appropriate, depending on the coating choice. Thehydrophilic coating may be any coating that bonds or attaches to theouter wall 44 and tip 50. The hydrophilic coating may be bond to outerwall 44 by any suitable, manner of attachment, such as physicalanchoring via an interpenetrating polymer network or by chemicalbonding. Such hydrophilic coatings may include for example,polyvinylpyrollidone, polyacrylic acid, polyvinylether maleic anhydridecopolymer, or other highly hydrophilic polymers and copolymers. In theconventional forming process, the process conditions need to be adjustedand controlled to keep the desired outer layer material on the surfaceof the formed tip.

It is believed that this process of tip forming will be a lower costoption compared to conventional forming with an induction heated die.

An alternate embodiment of the catheter of the present disclosure has anextruded tube that is cut to length for a catheter product. At one cutend, a formed tip is made by an insert micro-injection molding step asdescribed above. At the other end, a funnel is formed by a second insertinjection molding step. Prior art catheters having a funnel are made bycutting an extruded tube to length, forming a tip by forcing one of thecut ends into a heated die, followed by cooling of the die. Separately afunnel part is injection molded. Finally, the funnel part is assembledto the other tube end using solvent bonding. These tip forming steps andthe funnel solvent bonding steps involve a fair amount of labor cost,which is avoided by making the funnel-equipped catheter according to thepresent disclosure. The insert injection molded funnel can comprise lessmaterial compared to a conventional injection molded funnel that isassembled to an extruded tube. The methods described in this disclosureare more generally applicable to use of other materials, such ascoextruded tubes and materials that do not solvent bond well. Togetherthese can provide a fully converted catheter product, at meaningful costsavings.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modification can be madewithout departing from the spirit and scope of the invention disclosedherein.

Aspects of the present subject matter described above may be beneficialalone or in combination with one or more other aspects. Without limitingthe foregoing description, in accordance with one aspect of the subjectmatter herein, there is provided a catheter, which includes a length oftubing with an axial lumen defined therein. The lumen has an insidediameter and the tubing terminates at an end. A plug is inserted in thelumen a distance sufficient to axially recess the plug from the end ofthe tubing. At least a portion of the plug has a maximum outsidediameter at least as large as the inside diameter of the lumen. A tip isattached to an end of the tubing. The tip includes a stubshaft thatextends into the lumen and is joined to the plug at a plug-to-tip bondline.

In accordance with another aspect which may be used or combined with thepreceding aspect, the catheter of has a hydrophilic coating on theexterior surface of the tubing and tip.

In accordance with another aspect which may be used or combined with anyof the preceding aspects, the catheter is provided with tubing that hasan inner wall and an outer wall.

In accordance with another aspect which may be used or combined with anyof the preceding aspects, the tubing has an inner wall and an outer walland further includes a hydrophilic coating on the exterior surface ofthe outer wall and tip.

In accordance with another aspect which may be used or combined with anyof the preceding aspects, the plug has at least one tapered end.

In accordance with another aspect which may be used or combined with anyof the preceding aspects, the tip has an apex at the free end thereofwith a depression formed in the apex.

In accordance with another aspect, there is provided a catheter, whichincludes a length of tubing with an axial lumen defined therein. Thelumen has an inside diameter, and the tubing terminates at an end. Aplug is inserted in the lumen. At least a portion of the plug has amaximum outside diameter at least as large as the inside diameter of thelumen. A tip is attached to an end of the tubing. The tip has an apex atits end opposite the tubing end, with a depression formed in the apex.

In accordance with another aspect which may be used or combined with thepreceding aspect, the catheter tubing has an inner wall and an outerwall and a hydrophilic coating on the exterior surface of the outer walland tip.

In accordance with another aspect, there is provided a method of makinga catheter, including the steps of providing tubing having an axiallumen defined therein, the lumen having an inside diameter; cutting thetubing to the desired catheter length; forming a plug, at least aportion of the plug having an outside diameter at least as large as theinside diameter of the lumen; pre-heating the plug; inserting thepre-heated plug into the lumen at an end of the tubing; inserting theend of the tubing into an injection mold cavity; injecting moltenthermoplastic polymer material under pressure into the mold cavity;cooling the mold cavity so the molten thermoplastic polymer materialsolidifies and forms a tip bonded to the plug and to the tubing end; andremoving the tubing with the formed tip from the mold.

In another aspect which may be used or combined with the precedingaspect, the method may include the step of forming a depression in theapex of the tip.

In accordance with another aspect which may be used or combined with anyof the preceding two aspects, the step of inserting the pre-heated pluginto the lumen may be characterized by locating the plug so that itsouter end terminates flush with the end of the tubing.

In accordance with another aspect which may be used or combined with anyof the preceding ninth and tenth aspects, the step of inserting thepre-heated plug into the lumen is characterized by recessing the plugfrom the end of the tubing.

In accordance with another aspect, there is provided a method of makinga catheter, including the steps of providing tubing having an axiallumen defined therein, the lumen having an inside diameter and thetubing having an inner wall and an outer wall; cutting the tubing to thedesired catheter length; forming a plug, at least a portion of the plughaving an outside diameter at least as large as the inside diameter ofthe lumen; inserting the plug into the lumen at an end of the tubing;inserting the end of the tubing into an injection mold cavity; injectingmolten thermoplastic polymer material under pressure into the moldcavity; cooling the mold cavity so the molten thermoplastic polymermaterial solidifies and forms a tip bonded to the plug and to the tubingend; removing the tubing with the formed tip from the mold; and applyinga hydrophilic coating to the exterior of the tubing and tip.

In accordance with another aspect which may be used or combined with thepreceding aspect, the step of forming a depression in the apex of thetip.

In accordance with another aspect which may be used or combined with anyof the preceding two aspects, pre-heating the plug prior to inserting itinto the lumen.

In accordance with another aspect which may be used or combined with anyof the preceding three aspects, the step of inserting the pre-heatedplug into the lumen is characterized by locating the plug so that itsouter end terminates flush with the end of the tubing.

In accordance with another aspect which may be used or combined with anyof the second, third and fourth preceding aspects, the step of insertingthe pre-heated plug into the lumen is characterized by recessing theplug from the end of the tubing.

In accordance with another aspect, there is provided a urinary catheter,which includes a length of tubing with an axial urinary lumen definedtherein, the lumen having an inside diameter, and the tubing terminatingat an end. A plug is inserted in the urinary lumen, at least a portionof the plug having a maximum outside diameter at least as large as theinside diameter of the urinary lumen. A tip is attached to an end of thetubing, and is joined to the plug at a plug-to-tip bond line.

In accordance with another aspect which may be used or combined with thepreceding aspect, the plug terminates at the same location as the tubingend.

In accordance with another aspect which may be used or combined with thesecond preceding aspect, the plug may protrude from the tubing end.

In accordance with another aspect which may be used or combined with thethird preceding aspect, the plug may be axially recessed from the tubingend.

1. A catheter, comprising: a length of tubing with an axial lumendefined therein, the lumen having an inside diameter, the tubingterminating at an end; a plug inserted in the lumen a distancesufficient to axially recess the plug from the end of the tubing, atleast a portion of the plug having a maximum outside diameter at leastas large as the inside diameter of the lumen; and a tip attached to anend of the tubing, the tip including a stubshaft that extends into thelumen and is joined to the plug at a plug-to-tip bond line.
 2. Thecatheter of claim 1 further comprising a hydrophilic coating on theexterior surface of the tubing and tip.
 3. The catheter of claim 1wherein the tubing has an inner wall and an outer wall.
 4. The catheterof claim 1 wherein the tubing has an inner wall and an outer wall andfurther comprising a hydrophilic coating on the exterior surface of theouter wall and tip.
 5. The catheter of claim 1 wherein the plug has atleast one tapered end.
 6. The catheter of claim 1 wherein the tip has anapex at the free end thereof with a depression formed in the apex. 7.(canceled)
 8. (canceled)
 9. A method of making a catheter, comprisingthe steps of: a) providing tubing having an axial lumen defined therein,the lumen having an inside diameter; b) cutting the tubing to thedesired catheter length; c) forming a plug, at least a portion of theplug having an outside diameter at least as large as the inside diameterof the lumen; d) pre-heating the plug; e) inserting the pre-heated pluginto the lumen at an end of the tubing; f) inserting said end of thetubing into an injection mold cavity; g) injecting molten thermoplasticpolymer material under pressure into the mold h) cooling the mold cavityso the molten thermoplastic polymer material solidifies and forms a tipbonded to the plug and to the tubing end; and i) removing the tubingwith the formed tip from the mold.
 10. The method of claim 9 furthercomprising the step of forming a depression in the apex of the tip. 11.The method of claim 9 wherein the step of inserting the pre-heated pluginto the lumen is characterized by locating the plug so that its outerend terminates flush with the end of the tubing.
 12. The method of claim9 wherein the step of inserting the pre-heated plug into the lumen ischaracterized by recessing the plug from the end of the tubing. 13.(canceled)
 14. (canceled)
 15. (canceled)
 16. (canceled)
 17. (canceled)18. A urinary catheter, comprising: a length of tubing with an axialurinary lumen defined therein, the lumen having an inside diameter, thetubing terminating at an end; a plug inserted in the urinary lumen, atleast a portion of the plug having a maximum outside diameter at leastas large as the inside diameter of the urinary lumen; and a tip attachedto an end of the tubing, and joined to the plug at a plug-to-tip bondline.
 19. The urinary catheter of claim 18 wherein the plug terminatesat the same location as the tubing end.
 20. The urinary catheter ofclaim 18 wherein the plug protrudes from the tubing end.
 21. The urinarycatheter of claim 18 wherein the plug is axially recessed from thetubing end.
 22. The urinary catheter of claim 18 wherein the tip has anapex at its end opposite the tubing end, with a depression formed in theapex.